med gas vac system short

8/3/2019 Med Gas Vac System Short

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PSD

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Medical Gasand Vacuum

Systems

Continuing Education from Plumbing Systems & DesignKenneth G.Wentink, PE, CPD, and Robert D. Jackson

JANUARY/FEBRUARY 2006

PSDMAGAZINE.ORG


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GENErAl

Health care is in a constant state o change, which orces the

plumbing engineer tokeep upwithnew technology toprovideinnovative approaches to thedesign o medical-gas systems. Indesigningmedical-gasandvacuumsystems,thegoalistoprovideasaeandsufcientowatrequiredpressurestothemedical-gasoutletorinletterminalsserved.Systemdesignandlayoutshouldallowconvenientaccessbythemedicalstatooutlet/inlettermi-nals,valves,andequipmentduringpatientcareoremergencies.

Tis section ocuses on design parameters and current stan-dardsrequiredorthedesignononammablemedical-gasandvacuum systems used in therapeutic and anesthetic care. Teplumbingengineermustdeterminetheneedsothehealth-caresta.rytoworkcloselywiththemedicalstatoseekanswerstotheollowingundamentaldesignquestionsatthestartoaproj-ect:1. Howmanyoutlet/inletsarerequestedbysta?

2. Howmanyoutlet/inletsarerequired?

3. Basedoncurrentconditions,howotenistheoutlet/inletused?

4. Basedoncurrentconditions,whatistheaveragedurationouseoreachoutlet/inlet?

5. Whatistheproperusage(diversity)actortobeused?

MEDICAl-GASSySTEMDESIGNChECklIST

As any hospital acility mustbe specially designed to meet theapplicablelocalcoderequirementsandthehealth-careneedso

thecommunityitserves,themedical-gasandvacuumpipingsys-temsmustalsobedesignedtomeetthespecicrequirementsoeachhospital.

Followingaretheessentialstepstoawell-designedandunc-tionalmedical-gaspipedsystem,whicharerecommendedtotheplumbingengineer:1. Analyzeeachspecicareaothehealth-careacilitytodeter-

minetheollowingitems:A. Whichpipedmedical-gassystemsarerequired?B. Howmanyoeachdierenttypeomedical-gasoutlet/inlet

terminalarerequired?C. Whereshouldtheoutlet/inletterminalsbelocatedor

maximumefciencyandconvenience?

D. Whichtypeandstyleooutlet/inletterminalbestmeettheneedsothemedicalsta?

2. Anticipateanybuildingexpansionandplaninwhichdirec-tiontheexpansionwilltakeplace(verticallyorhorizontally).Determinehowthemedical-gassystemshouldbesizedand

valvedinordertoaccommodatetheutureexpansion.

3. Determinelocationsorthevariousmedical-gassupplysources.

A. Bulkoxygen(O2).B. High-pressurecylindermaniolds(O2,N2OorN2).

C. Vacuumpumps(VAC).D. Medical-aircompressors(MA).

4. Preparetheschematicpipinglayoutlocatingtheollowin

A. Zonevalves.B. Isolationvalves.C. Masteralarms.D. Areaalarms.

5. Calculatetheanticipatedpeakdemandsoreachmedicasystem.Appropriatelysizeeachparticularsectionsoastoavoidexceedingthemaximumpressuredropsallowed.

6. Sizeandselectthevariousmedical-gasandvacuumsuppequipmentthatwillhandlethepeakdemandsoreach

system,includingutureexpansions.Ithisprojectisanationtoanexistingacility,determinetheollowing:

A. Whatmedicalgasesarecurrentlyprovidedandwhatathelocationsandnumberothestations?

B. Canthecurrentgassupplier(orthehospitalspurchasdepartment)urnishtheconsumptionrecords?

C. Arethecapacitiesotheexistingmedical-gassupplystemsadequatetohandletheadditionaldemand?

D. Areanyexistingsystemsvalvedthatcouldbeusedorextension?Aretheexistingpipesizesadequatetohantheanticipatedadditionalloads?

E. Whattypeoequipmentisinuseandwhoisthemanuturer?Isthisequipmentstate-o-the-art?

F. IsiteasibletomanioldthenewandexistingequipmeG. WhatisthephysicalconditionotheexistingequipmeH. Isthereadequatespaceavailableorthenewmedical-

supplysystemsandrelatedequipmentattheexistingtion?

I. Isexistingequipmentscheduledtobereplaced?(Amatenancehistoryotheexistingequipmentmayhelpindetermination.)

NuMBEroFSTATIoNS

Terststepistolocateandcounttheoutlet/inlets,otencstations,oreachrespectivemedical-gassystem.Tisisusdonebyconsultingaprogrampreparedbytheacilityplann

architect.Tisprogramisalistoalltheroomsandareasiacilityandtheservicesthatarerequiredineach.Iaprogramnotbeenprepared,theoorplansortheproposedacilitybeused.

Tereisnocodethatspecicallymandatestheexactnumostationsthatmustbeprovidedinvariousareasorroomshealth-careacilities.Inact,thereisnoclearconsensusoopiamongmedicalauthoritiesordesignproessionalsastohowmstationsareactuallyrequiredintheacilityareas.Guidelines

CONTINUING EDUCAT

Medical Gas andVacuum Systems

Reprinted fromAmerican Society of Plumbing Engineers Data Book Volume 3: Special Plumbing Systems, Chapter 2: Medical Gas and VacSystems. 2000, American Society of Plumbing Engineers.

PlumbingSystems&Design JANUARY/FEBRUARY 2006 PSDMAGAZ


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publishedby the American Institute o Architects(AIA),NationalFireProtectionAssociation(NFPA),andASPEthatrecommendtheminimumnumberostationsorvariousservicesinspecicareas.

Te mostoten-usedrecommendations in deter-miningthenumberostationsorhospitalsarethosenecessarytobeaccreditedbytheJointCommissionor the Accreditation o Hospitals Organization(JCAHO).AccreditationisrequiredorMedicareandMedicaid compensation. Te JCAHO publishes a

manualthatreerstotheAIAguidelinesorthemini-mum number o stations or oxygen, medical air,andvacuumthatmustbeinstalledinordertoobtainaccreditation.Ithisisaactorortheacility,theserequirements are mandatory. Other jurisdictions,suchasstateorlocalauthorities,mayrequireplanstobeapprovedbylocalhealthorbuildingofcials.Tese approvalsmay require adhering to the stateorlocalrequirementsand/orNFPA99,Health-CareFacilities.

I accreditation or the approval o authorities isnotaactor,thenumberandarealocationsosta-tionsarenotmandated.Teactualcountthenwilldepend upon requirements determined by eachindividualacilityoranothermemberothedesignteam using both past experience and anticipateduture use, oten using the guideline recommenda-tionsasastartingpoint.

MEDICAl-GASFlowrATES

Eachstationmustprovideaminimumowrateortheproper unctioning o connected equipment underdesignandemergencyconditions.Teowratesanddiversity actors vary or individual stations in eachsystemdependingonthetotalnumberooutletsandthetypeocareprovided.

Teowrateromthetotalnumberooutlets,with-outregardoranydiversity,iscalledthetotalcon-nectedload.Ithetotalconnectedloadwereusedorsizingpurposes,theresultwouldbeavastlyoversizedsystem,sincenotallo thestationsintheacilitywillbeusedatthesametime.Adiversity,orsimultane-ous-useactor,isusedtoallowortheactthatnotallothestationswillbeusedatonce.Itisusedtoreducethesystemowrateinconjunctionwiththetotalcon-nectedloadorsizingmainsandbranchpipingtoallpartsothedistributionsystem.Tisactorvariesordierentareasthroughoutanyacility.

Teestimatedowrateanddiversityactorsorvarioussystems,areastations,andpiecesoequipmentareoundinable1.

otaldemandormedical-gassystemsvariesasaunctionotimeoday,month,patient-carerequirements,andacilitytype.Tenumberostationsneededorpatientcareissubjectiveandcannotbequaliedbasedonphysicalmeasurements.Knowingthetypesopatientcareand/orauthorityrequirementswillallowplacementostationsinusagegroups.Tesegroupscanestablishdemand and simultaneous-use actors (diversities), which areusedinthecalculationorsizingaparticularsystem.Allmedical-gaspipingsystemsmustbeclearly identiedusinganapprovedcolor-codingsystemsimilartothatshowninable2.

MEDICAl-GASSySTEMDISPENSINGEquIPMENT

Medical-gas outlet/inlet terminals Most manuacture

medical-gas system equipment oer various types o medgasoutlets.Tesemedical-gasoutletsareavailableinvariouorders(e.g.,O2-N2O-Air),center-linespacing,andorexposedconcealedmountings.OutlettypesandcongurationsmusttherequirementsothelocaljurisdictionalauthorityandN99.All outlets must be properly identiedandconrmed.shouldalsobetakentoaccuratelycoordinatethevariouspiecmedical-gasdispensingequipmentwiththearchitectandmedstainvolvedinthegivenproject.Itheprojectisarenovationoutlettypesshouldmatchexistingequipment.Withpreabripatientheadwallunits,themedical-gasoutletsaregenerallynishedbytheequipmentmanuacturer,anditis veryimpothatcoordinationbemaintainedbytheengineersothatunn

table 1 Outlet Rating Chart or Medical-Vacuum Piping Systems

Free-Air Allowance, cm(L/min) at 1 atmosphere

Zone Allowances CorrRisers, Main Supply Li

Valves

Location o Medical-Surgical VacuumOutlets Per Room Per Outlet

SimultaneousUsage Factor

(%)

Air toTranspocm (L/m

Operating rooms:Major A (Radical, open heart; organtransplant; radical thoracic) 3.5 (100) 100 3.5 (1Major B (All other major ORs) 2.0 (60) 100 2.0 Minor 1.0 (30) 100 1.0

Delivery rooms 1.0 (30) 100 1.0 Recovery room (post anesthesia) andintensive-care units (a minimum o 2outlets per bed in each such department):

1st outlet at each bed 3 (85) 50 1.5 2nd outlet at each bed 1.0 (30) 50 0.5 3rd outlet at each bed 1.0 (30) 10 0.1 All others at each bed 1.0 (30) 10 0.1

Emergency rooms 1.0 (30) 100 1.0 Patient rooms:

Surgical 1.0 (30) 50 0.5 Medical 1.0 (30) 10 0.1 Nurseries 1.0 (30) 10 0.1

Treatment & examining rooms 0.5 (15) 10 0.05 Autopsy 2.0 (60) 20 0.04

Inhalation therapy, central supply &instructional areas 1.0 (30) 10 0.1 a Free air at 1 atmosphere.

table 2 Color Coding or Piped Medical Gases

Gas Intended or Medical Use United States Color Canada Color

Oxygen Green Green on whitea

Carbon dioxide Gray Black on gray

Nitrous oxide Blue Silver on blue

Cyclopropane Orange Silver on orange

Helium Brown Silver on brown

Nitrogen Black Silver on black

Air Yellow* White and black on black and white

Vacuum White Silver on yellowa

Gas mixtures (other thanmixtures o oxygen and nitrogen)

Color marking o mixtures shall be a combination o colorcorresponding to each component gas.

Gas mixtures o oxygen andnitrogen

19.5 to 23.5% oxygenAll other oxygen concentrations

YellowaBlack and green

Black and whitePink

Source: Compressed Gas Association, Inc.a Historically, white has been used in the United S tates and yellow has been used in Canada to identiy vacuum systems.

Thereore, it is recommended that white notbe used in the United States and yell ow notbe used in Canada as a marking

to identiy containers or use with any medical gas. Other countries may have diering specifc requirements.

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CONTINUING EDUCATION: Medical Gas and vacuum Syste

saryduplicationoworkisavoided.Also,withregardtotheover-the-bed medical-gas service consoles, these consoles are otenspeciedintheelectricalorequipmentsectionothespecica-tionandmedical-gasserviceoutletsarespecied,urnished,andinstalledunderthemechanicalcontract.

Gas-outlet sequence, center-line spacing, and multiple-gang-service outlets are some o the considerations to be taken intoaccountwhenrequestinginormationromthevariousequipmentmanuacturers.Itismorepractical,intermsoboththecostotheequipmentandtheinstallation,tospeciyandselectthemanuac-

turersstandardoutlet(s).Detailsandspecicationsregardingtheindividualstandardoutletsareusuallyavailableromallmanuac-turersuponrequest.

Teexistingoutletsarecompatiblewiththeadaptersoundonthehospitalsanesthesiamachines,owmeters,vacuumregula-tors,etc.Careshouldbetakentomakesureallutureexpansionsinthesameacilityhavecompatibleequipment.

Patient head-wall systems A recent and growing trend inhospital construction is the requirement or patient head-wallsystems,whichincorporatemanyservicesor thepatientscare.Teseunitsmayincludetheollowing:1. Medical-gasoutlets.

2. Electrical-serviceoutlets(includingemergencypower).3. Directandindirectlighting.

4. Nurse-callsystem.

5. Isolationtransormers.

6. Groundingoutlets.

7. Patient-monitoringreceptacles.

8. VacuumslideandIVbrackets.

9. Nightlights.

10.Electricalswitches.

Bed locator units are also available, which serve to providepowerorthemoreadvancedpatientbeds,telephone,nightlights,

and standard power. Tese unitsalso unction to protect the wallsrom damage as beds are movedandadjusted.

Head walls currently vary inshape, size, type, and cost rom asimple over-the-patient-bed stan-dard conguration to elaboratetotal-wallunits.Mostmanuactur-ersomedical-gasequipmentoermedical-gas outlets or all typeso patient consoles available intodays market. When speciying

head-walls outlets, the plumbingengineer should consider the ol-lowing:1. Istheserviceoutletselected

compatiblewiththeexistingoutletcomponent?

2. Doesthepatienthead-wallmanuacturerincludethetypeomedical-gasoutletsrequiredaspartotheproduct?

Special types of ceiling-mounted, medical-gas out-

lets In critical-care areas, which are generally consideremostindividualstobethoselocationsothehospitalprovidspecialtreatmentorserviceorthepatient(suchassurgery,reery,coronary,orintensive-careunits),thedesignersselectionplacementothemedical-gasserviceequipmentmustbed

verycareullyinordertoprovideefcientworkcentersarounpatientorthemedicalsta.

Manuacturers omedical-gasservice equipmentusuallyvideawiderangeoequipmentthatisavailableoruseinareas.Dependinguponthecustomerspreerenceandthea

ablebudget,theequipmentisselectedtoprovidetheneceindividualgasservicesandaccessories.

able3providesaquickreerenceguideortheengineertasabasisorselectingthecommonlyusedtypesooutletdispingequipment.

Example 1Te ollowing illustrative example presentssomeo the

importantcritical-careareaequipmentandoptionsorthestionotheequipment.

Surgerymedical-gasservicestobepipedinclude:1. Oxygen.

2. Nitrousoxide.

3. Nitrogen.4. Medicalcompressedair.

5. Vacuum.

6. Wasteanesthetic-gasdisposal.

Providingmedical-gasserviceoutletsinthesurgeryroombeaccomplishedinseveralways,suchastheollowing:1. Ceiling outletsIndividualmedical-gasoutletsmountedin

ceilingwithhoseassembliesprovidingthemedicalstawconnectionsromtheoutletstotheadministeringappara

Tismethodisconsideredbymosttobethemosteconomcalmeansoprovidinganadequategasservicetothesur

table 3 Types o Dispensing Equipment or Specifc Areas

Hospital Areas

Medical Gas Outlet Dispensing Equipment

Wall-MountedOutlets

PatientCare Head

Wall

Ceiling-Mounted

Outlets withHose Stops

RigidCeiling

Columns

RetractableCeiling

Columns

Ceilingwith Gas

Stacks

NitrCon

CabAutopsy rooms Delivery rooms Emergency examination and treatmentrooms

Emergency operating rooms Induction rooms Labor rooms Major surgery rooms

Minor surgery, cystoscopy Neonatal intensive care units Normal nursery rooms Nursery workrooms O.B. recovery rooms Patient rooms Pediatric and youth intensive care unit Post-operative recovery rooms Premature and pediatric nursery rooms Pre-op holding rooms Radiology rooms Respiratory care unit Specialized surgeries (cardiac and neuro)



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areas.Teceilinggas-serviceoutletsaregenerallylocatedatboththeheadandtheoototheoperatingtableinordertoprovidealternatepositioningotheoperatingtable.

2. Surgical ceiling columns Surgicalceilingcolumnsareusu-allyavailableintwodesigns:rigid(apredeterminedlengthromtheceilingheightabovetheoor)andretractable.Bothsurgicalceilingcolumnsprovidemedical-gasserviceswithinanenclosurethatprojectsdownromtheceiling.Teceilingcolumnsareusuallylocatedatoppositeendsotheoperatingtableinordertoprovideconvenientaccesstothemedical-gasoutletsbytheanesthesiologist.Inadditiontothemedical-gasoutlets,theseceilingcolumnscanbeequippedwithelectri-caloutlets,groundingreceptacles,physiologicalmonitorreceptacles,andhooksorhangingintravenous-solutionbottles.

Mostmanuacturersoeringsurgicalceilingcolumnsallowormanyvariationsinroomarrangementsomedical-gasservicesandrelatedaccessories,dependinguponthespeciccustomersneedsandtheengineersspecications.Whenspeciyingthistypeoequipment,itisnecessarytospeciycareullyallmedical-gasservicerequirementsandtheirdesiredarrangement(s).Also,theengineermustcoordinateallotherrequiredserviceswiththe

electricalengineerandmedicalsta.3. Surgical gas tracks Surgicalgastracksareormsoceiling

outletandhose-droparrangementsthatallowthemovementothehosedropsromoneendotheoperatingtabletotheotheronslidingtracksmountedontheceiling.Teseprod-uctsarecurrentlyavailableromvariousmanuacturersandallprovidethesamebasicservices.Teproperselectionandspecicationospecictypesarebasedonindividualcus-tomerpreerence.Manyvariationsinproductsandparticularproductapplicationsareavailableincritical(intensive)careareas.Consultationwithappropriatemanuacturersorrec-ommendationsisalwaysadvisable.

4. Articulating ceiling-service centerArticulatedceiling-ser-vicecentersaremovedbypneumaticdrivesystemsandaredesignedortheconvenientdispensingomedical-gasandelectricalservicesinoperatingrooms.Temedical-gasandelectricalsystemsarecompleteorsingle-pointconnectiontoeachoutletatthemountingsupportplatorm.

High-pressure nitrogen (N2) dispensing equipment Specialconsideration must be given by the plumbing engineer to theplacementothenitrogenoutlets.Teprimaryuseonitrogengasinhospitalsisordrivingturbo-surgicalinstruments.Variationsotheseturbo-surgicalinstruments,inboththeirmanuactureandtheirintendeduse,willrequirethatseveraldierentnitrogen-gaspressurelevelsbeavailable.Forthisreason,itisnecessarythat

the engineer provide an adjustable pressure-regulating devicenearthenitrogengasoutlet.Anitrogencontrolpanelisusuallylocatedonthewall(inthesurgeryroom)oppositetheoperatingareasterileeld.Teinstallationshouldallowortheaccessandadjustmentopressuresettingsbyasurgicalnurse.

Pipingromthenitrogencontrolpaneltoasurgicalceilingoutletwillprovideaconvenientsourceonitrogenorsurgicaltools.Tiswillpreventhosesrombeinglocatedontheoororbetweenthewalloutletandtheoperatingtable.Excesshosecanbeobstructivetothesurgicalteam.

MEDICAl-GASSTorAGE

Aterdecidingthemedical-gasservicestobeprovidedattheity, the engineer should determine thestorage capacity anpipe sizingrequiredandpossible locationsor thesource.codesandreerencesaswellastheadministrativeauthorityha

jurisdictionshouldbeconsultedoreachmedical-gassystem.Because o the unique characteristics o each medica

source, the gases aredescribed separately in thissection.anexplanationo thetechniquescurrentlyemployedto exhanestheticgasesisprovided.

Oxygen (O2) Severalactorsmustbeknownwhenestimthe monthly consumption o oxygen in new or existing hecareacilities:1. ypeomedicalcareprovided.

2. Numberooxygenoutletsor

3. Numberopatientbeds.

4. Futureexpansionoacility.

5. Inexistingacilities,approximateconsumption.

wo methods can beusedby the plumbing engineer tomatetheconsumptionooxygen.Temoreaccuratemethodobtainadetailedconsumptionrecordromthehealth-careacorobtainmonthlyoxygenshipmentinvoicesromthesupplinventoryrecordsarenotavailableromthehealth-careacilthesupplier,use consumptionrecords rom acomparablyacility,withgoodjudgment.

Tesecondmethodistoapplytheollowingruleothumestimatethemonthlysupplyooxygen.Tisestimatingmeshouldbeusedwithgoodjudgment.Alwayscoordinateestimdemandwiththeoxygensupplierduringthedesignprocess1. Innon-acute-careareas,allow500t3(14m3)perbedper

monthorsupplyandreserveoxygenstorage.

2. Inacute-careareas,allow1000t3(28m3)perbedpermoorsupplyandreserveoxygenstorage.

Oxygensupplysourcesaredividedintotwocategories:(1)

oxygensystemsand(2)cylinder-maniold-supplysystems.Boxygen systems should be considered or health-care ac

withanestimatedmonthlydemandabove35,000t3(991mequalto70oxygenoutlets.Manioldsystemsareusedinsmgeneralhospitalsorclinics.

Bulk-oxygen systems Whenselectingandplacingbulk-oxsystems,thereareseveralactorstobeconsidered:Oxygentporttrucksize,truckaccesstobulk-storagetanks,andNFPStandard or Bulk Oxygen Systems at Consumer Sites.Bulk-oxequipment,construction,installation,andlocationmustco

with NFPA 50 recommendations. I liquid oxygen is spillleaked,anextremereorexplosivehazardcouldoccur.NFPAdesignstandardstominimizereexposuretoandromsurrouingstructures.

Bulk-storagesystemsconsistocryogenictanksthatstoreloxygenat lowpressures(225psi [1551.3kPa]orless).CryotanksareASMEunred,double-walled,vacuum-insulated,surevessels.Liquidoxygenhasa boilingpoint(nbp)o29(182.9C) and a liquid density o 71.27 lb/t3 (1141.8 kg/

Whenvaporizedintogas,itproduces900timesitsliquidvolFurthermore,sincethetankischangedlessoten,processstityismaximizedandtheintroductionoatmosphericimpuisreduced.anksystemsareurnishedwithanintegralpresrelie valve vented to the atmosphere should the liquid oxconverttoagas.



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Most bulk-oxygen storage systems are urnished with vapor-izers. Vaporizersarebanks o nned-tube heatexchangers thatconverttheliquidtoitsgaseousstate.Tevaporizerscomeinsev-eral stylesincluding atmospheric, powered (orced-air, steam,and electric), waste-heat, and hybridand sizes. Te selec-tion ovaporizers should bebased on demand, intermittent orcontinuous usage, energy costs,and temperature zones. Poorlyventilated sites or undersizedheat exchangers cancause ice toormonvaporizersduringtheconversionprocess.Excessiveiceormations can clog and damage the vaporizer. Also, ice couldallowextremelycoldgasorthecryogenicliquidtoenterthepipedsystem; damage the valves, alarms, and medical components;andeveninjurepatients.Figure1illustratesatypicalbulk-oxygensystemschematic.

Automaticcontrolsurnishedwiththetanksregulatetheowoliquidthroughthevaporizers.Whenthereisademandoroxygen,thesupplysystemdrawsliquidromthebottomothecryogenicstoragetankthroughthevaporizers.Tegasmovesthroughanal

line regulator. Tus, a constant supply o oxygen at a regulatedpressureisprovided.Incaseomechanicaldifcultyorthedepletionotheliquid-

oxygensupply,thereservesupplywillbegintoeedintothedistri-butionsystemautomatically.

An alarm signal should alert appropriate hospital personnelwhenthe liquid inthe oxygenstorage tank reachesa predeter-minedlevel.Te alarmsignalsshouldindicatelowliquidlevels,reserveinuse,andreservelow.

Cylinder-manifold supply systems Compressed-oxygensystems are comprised o cylinder maniolds that allow a pri-marysupplysourceooxygencylinderstobeinuseandanequalnumberooxygencylinderstobeconnectedasareservesupply.

Tecontrolsothecylindermanioldwillautomaticallyshiowotheoxygengasromtheservicesidetothereserve

whentheservicesideisdepleted.Maniold systems can be located indoors or outdoors. W

manioldsarelocatedindoors,theengineershouldobservollowing: Location Preerably,themanioldshouldbeinadedicat

roomonanoutsidewallnearaloadingdockandhaveadquateventilationandserviceconvenience.

Adjacent areas Tereshouldbenodoors,vents,orotherdirectcommunicationsbetweentheanesthetizinglocatiothestoragelocationandanycombustibleagents.Ilocatinearoradjacenttoanelevatedtemperatureareaisunavoable,theengineershouldspeciysufcientinsulationtop

ventcylinderoverheating;

Fire rating Tere-resistanceratingotheroomshouldbleast1h.

Ventilation Outsideventilationisrequired.

Security Teroom(orarea)mustbeprovidedwithadoogatethatcanbelockedandlabeled.

Oxygenmanioldsaresizedtakingintoconsiderationthelowing:1. Tesizeothecylinders,244t3(6909L)H-cylinder(see

4orasizingchart).

2. Tehospitalsusageooxygen,int3(L)permonth.

Figure 1 Typical Bulk Supply System (Schematic)



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table 4 Selection Chart or Oxygen Maniolds

Hospital Usage Duplex Maniold Size

Cu. Ft. (103 L) per month Total Cylinders Cylinders per Side

5,856 (165.8) 6 3

9,760 (276.4) 10 5

13,664 (386.9) 14 7

17,568 (497.5) 18 9

21,472 (608.0) 22 11

25,376 (718.6) 26 1329,280 (829.1) 30 15

33,154 (938.8) 34 17

Note: Based on use o 244 t3 (6909.35 L) H-cylinders.

Nitrous oxide(N2O) Tecommonsourceonitrousoxideisacylinder-manioldsystem.High-pressuremanioldsystemscon-sistotwobanksocylinders,primaryandreserve.(Seediscus-sionunderOxygen,above.)

Systemdemandsornitrousoxidecanbemoredifculttodeter-minethantheyareorothermedicalgases.Tenumberosurger-iesscheduled,thetypesandlengthsosurgery,andtheadmin-isteringtechniques usedbytheanesthesiologistscause extremevariations in theamount o nitrousoxideused. Becauseo thisvariation,considerationsmustbegiventothesizeandselectionothenitrous-oxidemanioldsystem.

Avoid locating the nitrous-oxide maniold system outdoors inareaswithextremelycoldclimates.Nitrousoxideissuppliedlique-edatitsvaporpressure o745psi(5136.6kPa)at70F(21.1C).At extremely cold temperatures, the cylinder pressure will dropdramatically,reducingthecylinderpressuretoapointwhereitisimpossibletomaintainanadequatelinepressure.Tisisduetoalackoheatorvaporization.

Fornitrous-oxidemanioldslocatedindoors,thesameprecau-tionspreviouslylistedoroxygensystemsmustbeobserved.

Teollowingshouldbeconsideredwhenselectingandsizing

nitrous-oxidemanioldsanddeterminingthenumberocylindersrequired:1. Tesizeothecylinders:489t3(13847L)K-cylinders(see

able5).

2. Tenumberoanesthetizinglocationsoroperatingrooms.

3. Provideo1cylinderperoperatingroomorin-serviceandreservesupplies.

table 5 Sizing Chart or Nitrous Oxide Cylinder Maniolds

Number oOperating

Rooms

Duplex Maniold Size

Indoor Outdoor

Total CylindersCylinders per

Side Total CylindersCylinders per

Side

4 4 2 4 28 8 4 10 5

10 10 5 12 5

12 12 6 14 7

16 16 8 20 10Note: Based on use o 489 t3 (13.85 103 L) K-cylinders.

Medical compressed air Medical compressed air may besupplied by two types o system: (1) a high-pressure cylinder-manioldsystem;and(2)amedicalair-compressorsystem.

Temanioldsystemsorcompressedairaresimilarincongu-rationtothoseoroxygenandnitrousoxide(seediscussionunderOxygen, above). Air supplied romcylinders or that hasbeen

reconstitutedromoxygenU.S.P.andnitrogenN.F.mustcomasaminimum,withGradeDinANSIZE86.I, Commodity Spcation or Air.

Medical compressed air can be produced on site rom aspheric air using air compressors designed or medical apptions.Terearethreemajortypesoaircompressorinthemaplacetoday: thecentriugal,reciprocating,and rotaryscrewreciprocating and rotary screw are positive-displacementunits,whilethecentriugalcompressorisadynamictypecpressor.Temedicalaircompressorshallbedesignedtopre

theintroductionocontaminantsorliquidintothepipelinebyotwomethods:ype1aircompressorseliminateoilanywhethecompressor.ype2aircompressorsseparatetheoil-contasectionromthecompressionchamber.Examplesoatype1cpressoraretheliquidring,rotaryscrew,andpermanentlysebearingcompressor.ype2compressorshaveextendedhead

Apositive-displacementcompressorisnormallyratedinacubiceetperminute(acm).Tisistheamountoairtakenatmosphericconditionsthattheunitwilldeliveratitsdischa

Withinabroadrange,changesininletairtemperature,presandhumiditydonotchangetheacmratingoeitherthereccatingor therotaryscrewcompressor.Te centriugalcomsorscapacity,however,isaectedslightlybytheinletaircotionsduetothenatureothecompressionprocess.Forexamas the air temperature decreases, the capacity o the dyncompressorwillincrease.Tecapacityo acentriugalcomsorisnormallydenedininletcubiceetperminute(icm).eorttoobtainanapplestoapplescomparisonovariouspressors,manymanuacturersspeciytheircapacityrequireminstandardcubiceetperminute(scm).Tissometimescamuch conusionbecausemany people do not ully undershowtoconvertromacmoricmtoscm.Tedesignenginspeciying scm must dene a typical inlet air condition abuildingsiteandtheirsetostandardconditions(normallypsia[101.4kPa],60F[15.6C],and0%relativehumidity).

cally,thewarmestnormalconditionisspeciedbecauseatemperaturegoesupscmwillgodown.oconvertromacmtoscm,theollowingequationisus

Equation 1

scm =acmPi(Ppi%RH) std

Pstd(Ppstd%RHstd) iwhere Pi=Initialpressure Ppi=Partialinitialpressureowatervaporin100%humid

thetemperatureinquestion RH=Relativehumidity Pstd=Pressureunderstandardconditions Ppstd=Partialstandardpressureowatervaporin100%hum

airatthetemperatureinquestionRHstd=Relativehumidityatstandardconditions std=emperatureatstandardconditions,F(C) i=Inlettemperature,F(C)



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Equation 1aTisequationisderivedromthePerectGaslaw,whichis:

P1V1 =P2V2

1 2or:

V2=V1P1 2P2 1

whereP1=InitialpressureV1=Initialvolume1=Initialtemperature

P2=FinalpressureV2=Finalvolume2=Finaltemperature

Forareciprocatingorrotary-screwcompressor,theconversionromacmtoscmissimple.Teinletairconditionsandstandardconditions are inserted into the above ormula and multipliedbytheacmcapacityotheunit.Itmakesnodierencewhatthedesignconditionsareorthatcompressor,asthesedonotgureintotheormula.Inthecaseoadynamiccompressor,theicmairowatthegiveninletconditionsisinsertedinplaceotheacmintheormula.Anotherdesignissuethattheengineershouldbeawareo ishowaltitudeaectstheoutputo thecompressor.At

altitudes above sea level, all medical-air systems have reducedow.Inthesecases,therequiredsizingwillneedtobeadjustedtocompensate.odothis,multiplythescmrequirementsbythecorrectionactorinable6.

table 6 Altitude Correction Factors or Medical-Air Systems

Altitude, t (m)Normal Barometric

Pressure, in. Hg (mm Hg)

CorrectionFactor or SCFM

(L/min)

Sea level 29.92 (759.97) 1.0 (28.31)

1,000 (304.8) 28.86 (733.04) 1.01 (28.6)

2,000 (609.6) 27.82 (706.63) 1.03 (29.16)

3,000 (914.4) 26.82 (681.23) 1.05 (29.73)

4,000 (1219.2) 25.84 (656.33) 1.06 (30.01)5,000 (1524) 24.90 (632.46) 1.08 (30.58)

6,000 (1828.8) 23.98 (609.09) 1.10 (31.14)

7,000 (2133.6) 23.09 (586.48) 1.12 (31.71)

8,000 (2438.4) 22.23 (564.64) 1.15 (32.56)

9,000 (2743.2) 21.39 (543.3) 1.17 (33.13)

10,000 (3048) 20.58 (522.7) 1.19 (33.69)

In other words, to correctly size the medical-air system, youwouldapplythecorrectionactorlistedinthechartabovetothepeak-calculatedload(scm)atsealevel.

Example 2Aacilityislocatedat5000t(1524m)abovesealevelandthesystemdemandis29.4SCFM.akethe29.4scmandmultiplyitby1.08(correctionactorromable5)togettheadjustedscmrequire-mento31.8scmat5000tabovesealevel.Tereore,amedical-airsystemogreatercapacityisneededathigheraltitudes.

Anotherhandyormulaorcompressed-airsystemsistheol-lowing:toconvertscmtoL/minmultiplyby28.31685.

Each compressor must becapableomaintaining 100% othemedical-airpeakdemandregardlessothestandbycompressorsoperating status. Tebasiccompressor package consistsolterintakes, duplex compressors, ater-coolers, receiving tanks, air

dryers,in-linelters,regulators,dew-pointmonitors,andvaTecompressorcomponentsareconnectedbypipingthataequipmentisolation, provides pressure relie,and removesdensateromreceivers.Medical-aircompressorsmustdrawsideairromabovetheroolevel,remoteromanydoors,windandexhaustorventopenings.Wheretheoutsideatmosphericpolluted,speciallterscanbeattachedtothecompressorsinto remove carbon monoxide and other contaminants. ReNFPA99orproperlocationomedical-airintakes.MedicalpressedairmustcomplywithNFPA99and/orCanadianStan

Associations(CSAs)denitionoair-qualitystandards.Wheremorethantwounitsareprovidedortheacility,an

unitsmustbecapableosupplyingthepeakcalculateddemProvide automatic alternators (duty-cycling controls) to enevenwearinnormalusage.Alternatorcontrolsincorporateaptivemeansoautomaticallyactivatingtheadditionalunit(orushouldthein-servicepumpailtomaintaintheminimumreqpressure.

Medical compressed air produced by compressors madenedasoutsideatmospheretowhichnocontaminants(iormoparticulatematter,odors,oilvapors,orothergases)beenaddedbythecompressorsystem.Noteverycompresssuitableoruseasasourceormedicalcompressedairinhecareacilities.Onlythosecompressorunitsspecicallydesigandmanuacturedormedicalpurposesshouldbeconsiderareliablesourceooil-ree,moisture-ree,andlow-tempercompressedair.Acceptablecompressortypesincludeoil-reeless,and liquid-ringcompressors.Separationo theoil-coningsectionromthecompressionchamberbyatleasttwoserequiredbythecompressormanuacturers.

Aircompressedormedical-breathingpurposesaretobeorthispurposeonlyandshouldnotbeusedorotherapptionsorcross-connectedwithothercompressedairsystems

table 7 Minimum Pipe Sizes or Medical Air-Compressor Intake Risers

Pipe size, in.

(mm)

Flow rate, cm

(L/min)2.5 (63.5) 50 (1416)

3 (76.2) 70 (1985)

4 (101.6) 210 (5950)

5 (127.0) 400 (11330)

able7providestheminimumpipesizesormedicalair-cpressorintakerisers.Consultwiththecompressormanuacton intake recommendations and allowable riction loss ointakeriserbeorenalizingthepipesizeequipmentselectio

0 Pl bi S t & D i JANUARY/FEBRUARY 2006 PSDMAGAZ

med gas vac system short

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